The germination of spores of the topical fungus Botryodiplodia theobromae may be used as a convenient experimental system for biochemical study of mitochondrial biogenesis in cells undergoing a developmental transition. The general objective of this proposed research is to study the respective contributions of the nuclear and mitochondrial genetic systems to the assembly and function of mitochondria as these spores complete synchronized germination. As a paradigm for the organization of the mitochondrial respiratory apparatus, we will study the biosynthesis and assembly of the mitochondrial enzyme cytochrome c oxidase, a multi-component respiratory enzyme whose subunits are derived from both cytoplasmic and mitochondrial ribosomes. A method will be developed for purification of cytochrome c oxidase, and this enzyme will be characterized with respect to its molecular weight, subunit composition, and quantity of heme a. Experiments will be conducted to establish whether any of the subunit proteins can be degraded or converted further into smaller hydrophobic polypeptides. By use of cycloheximide and chloramphenicol, chemical inhibitors of the cytoplasmic and mitochondrial ribosomes, respectively, we will determine the ribosomal origin of each of the cytochrome c oxidase subunit proteins in pulse-labeled spores, and we will establish the kinetics and timing of synthesis of the enzyme subunits during spore germination. Experiments will be conducted to establish which of the enzyme subunits are stored in the spore during dormancy and which of them are synthesized early in the germination sequence.